1. Field of the Invention
This invention relates to a method and apparatus for preparing a metal-ceramic composite body by impregnating a porous ceramic preform with a molten metal. More particularly, it relates to such a method and apparatus which facilitates impregnation of porous ceramic preforms of various shapes with molten metal while controlling the feed and feed rate of molten metal, thereby producing a metal-ceramic composite body without flaw.
2. Prior Art
Composite products of ceramic and metal are generally prepared by manufacturing porous ceramic preforms and impregnating the preforms with molten metal.
One of the simplest methods for supplying molten metal to preforms for impregnation is by containing molten metal in a crucible, placing a preform above the crucible, and bringing the preform in contact with the molten metal whereby the preform is entirely impregnated with the molten metal by utilizing the capillary phenomenon associated with micropores or interconnected cells in the preform. This method suffers from several problems.
(a) When a multiplicity of relatively small size preforms are impregnated at once, it is difficult to arrange a multiplicity of preforms such that all the preforms may be uniformly impregnated with molten metal. PA1 (b) Since preforms are impregnated with molten metal by utilizing the capillary phenomenon of the preforms, it is impossible to obtain composite products using preforms having a height exceeding a certain limit. PA1 (c) If exothermic reaction accompanies when preforms are impregnated with molten metal, many preforms can be damaged. PA1 (d) Often more metal is adhered to the outside, especially the bottom of a product, rendering post-treatment difficult. PA1 (e) The method is not suited for large scale manufacture since a container is necessary for each of products. PA1 (f) Where a plurality of preforms are disposed in a container and impregnated with molten metal, the preforms are at least partially submerged in the molten metal. The molten metal adheres to the outside of the resulting composite body. A difficult post-treatment is necessary to remove the metal deposit from the composite body after cooling and solidification. PA1 (g) Where it is desired to impregnate a cylindrical preform of a substantial length with molten metal, it is almost impossible to place the metal at the top of the preform because the metal is melted. The metal is naturally placed below the preform, which gives rise to problems similar to the above-mentioned problems (a), (b), and (c).
Another method is described in the Journal "ADVANCED MATERIAL AND PROCESSES", 7/91, p. 25. A metal to be infiltrated (single metal or alloy) is placed in a suitable container, the metal is disposed adjacent to the top or bottom of a preform, and the container is heated to melt the metal whereby the preform is impregnated with the molten metal. This method also suffers from several problems.